The present invention relates to a method for producing an optical transmitting and detecting device including a light-emitting transmitting element as well as a detecting element to convert this light into an electrical quantity, the transmitting and detecting element being incorporated into a silicon substrate.
A known approach exists in which this type of transmitting and detecting system is arranged sequentially on a frame to form an optocoupler, but the approach is complex due to the associated process of bending and precise assignment. Electrical insulation is created between the transmitting and detecting systems by providing, for example, an intermediary plastic or lacquer or similarly optically-transparent material.
The publication by S. M. Sze, Physics of Semiconductor Devices, 2nd edition, page 699 discloses an optocoupler which has an LED as the optical transmitting element and a silicon phototransistor as the light detector arranged on both sides of a glass insulator. Here again, a complex assembly technology is required both for production and for aligning an optical coupling which significantly affects the cost of production.
Optical transmitting elements (LEDs) are constructed on the basis of gallium arsenide, gallium arsenide phosphide, or gallium phosphide due in part to the high efficiency achieved. However, a disadvantage of these compound semiconductors is their poor mechanical properties in comparison to silicon, as well as the problem of integration into silicon-based systems.
To integrate optical systems based on GaAs, GaAsP, or GaP, the approach has also been suggested of incorporating a receptacle recess in the silicon substrate in which the optical system is then inserted and, for example, joined to the silicon system by bonding. An optical link can then be created, for example, by lateral emission from the optical gallium arsenide system to the silicon system. This approach too requires a complex assembly technology.
The publication Sensors and Actuators A 31 (1992) pp. 229-240 discloses an optocoupler in which the light source is an avalanche silicon diode. The optocoupler has arranged adjacent to one another on a substrate the avalanche diode as the light source and the light detector in the form of a photodiode. This arrangement requires a comparatively large chip surface area. In addition, the transmitter and detector are not dielectrically separated. Finally, certain measures are required to facilitate the lowest-possible-loss transmission of light between the transmitter and the detector another factor increasing the complexity of production.
Therefore, there is a need for a relatively low cost optical transmitting and detecting device, as well as a device that utilizes a relatively small amount of chip area, and a method of producing such a device.